Traditionally, disposable absorbent garments such as infant diapers or training pants and adult incontinence briefs are constructed with a moisture-impervious outer, or backing, sheet, a moisture-pervious body-contacting inner, or liner, sheet, and a moisture-absorbent core sandwiched and encased between the liner and backing sheets.
Much effort has been expended to find cost-effective materials for absorbent cores that display good liquid absorbency and retention. Superabsorbent materials in the form of granules, beads, fibers, etc., have been favored for such purposes. Such superabsorbent materials are generally polymeric gelling materials that are capable of absorbing large quantities of liquids such as water and body wastes relative to their weight and of retaining such absorbed materials even under moderate pressure.
The ability of a superabsorbent material to absorb liquid is dependent upon the form, position, and/or manner in which particles of the superabsorbent are incorporated into the absorbent core. Whenever a particle of the superabsorbent material in an absorbent core is wetted, it swells and forms a gel. Gel formation can block liquid transmission into the interior of the absorbent core, a phenomenon called "gel blocking." Gel blocking in and adjacent a zone in an absorbent core of initial liquid contact prevents liquid from rapidly diffusing or wicking past the "blocking" particles of superabsorbent into the rest of the absorbent core; further imbibition of liquid by the absorbent core must then take place via a diffusion process that can be much slower than the rate at which liquid is applied to the core. Gel blocking can thus result in leakage from the absorbent article well before the absorbent core is fully saturated.
Efficient imbibition of liquid by the absorbent core at the point of initial liquid contact and rapid distribution of the liquid away from this point is necessary to insure that the absorbent core has sufficient capacity to absorb subsequently deposited liquids. What is needed is an absorbent core that quickly imbibes and distributes large quantities of liquids throughout the core while minimizing gel blocking during initial liquid contact.
Preferably, the absorbent core is also thin in order to improve the appearance of a garment with such an absorbent core and the comfort of the wearer of the garment. The importance of thin, comfortable garments is disclosed, for example, in U.S. Pat. No. 5,098,423 (Pieniak et al.), which is incorporated herein by reference.